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Abstract

Background The goal of the present study was to determine the intermediate-term survival and the independent predictors of survival and event-free survival for patients who undergo catheter balloon commissurotomy (CBC).

Methods and Results CBC for the treatment of mitral stenosis was performed in 132 patients from 1986 through 1994. The use of CBC increased the mitral valve area (MVA) from 1.0±0.3 to 1.9±0.6 cm2 (P<.001). There were six early deaths (4.5%) up to 1 month after CBC (“hospital” deaths). In the past 4.5 years, there have been no hospital deaths. Four late deaths occurred after elective mitral valve replacement (MVR). Actuarial 7-year survival was 95±1%; when mortality after MVR is included, 7-year survival was 83±6%. Actuarial 1-, 3-, 5-, and 7-year event-free survival (survival without MVR or repeat CBC) was 80±4%, 77±4%, 65±6%, and 65±6%. On multivariate analysis, the only two independent predictors (both after CBC) of 7-year event-free survival were MVA of ≥1.5 versus <1.5 cm2 (75±7% versus 32±12%) and mean pulmonary artery wedge pressure of ≤18 versus >18 mm Hg (84±6% versus 38±11%) (P<.001 for both). Patients with MVA of ≥1.5 cm2 (n=96) could be further subdivided into high- and low-risk subgroups for 7-year event-free survival by two post-CBC variables: mean pulmonary artery wedge pressure of ≤18 versus >18 mm Hg (90±6% versus 48±14%) (P=.0002) and cardiac index of ≥2.5 versus <2.5 L·min−1·m−2 (82±8% versus 61±13%) (P=.004). Patients with post-CBC MVA of <1.5 cm2 (n=24) had no additional predictors of event-free survival. Of patients who did not undergo MVR or repeat CBC, 8% were in New York Heart Association functional class III and 92% were in class I or early class II at the last follow-up.

Conclusions The rates for intermediate-term survival and event-free survival after CBC are very encouraging. Most patients without events were asymptomatic or minimally symptomatic. Thus, in selected patients with mitral stenosis who require an interventional procedure, CBC is the procedure of choice at centers with physicians who have experience and skill in performing this procedure.

The use of CBC for MS in adults was reported by Inoue et al in 19841 and for children and adolescents by Lock et al in 1985.2 Al Zaibag et al3 reported the use of the double-balloon technique in 1986; subsequently, the Inoue balloon became available for percutaneous use.4 The encouraging very early experience5 in small numbers of patients was confirmed in subsequent studies. CBC has been documented to result in an immediate reduction in LAP and PAP and increases in CO and MVA.678 These beneficial effects persisted at follow-up both at rest and on exercise, and the patients were symptomatically improved.9 Subsequently, randomized trials have documented that the early results of CBC were similar to those obtained with closed or open surgical valvotomy.10111213 The early results and complications of CBC have been reviewed extensively, and follow-up data are available.141516171819202122 The goals of the present study were to determine the intermediate-term survival and event-free survival (≤7 years) and to identify predictors of intermediate-term survival and event-free survival.

Methods

Study Population

Between February 1986 and June 1994, CBC was attempted in 132 patients with MS at LAC+USC Medical Center. These 132 patients included all patients in whom CBC was attempted. The protocol was approved by our institutional review board, and written informed consent was obtained from all patients. The study group included 104 women and 28 men (mean±SD age, 44±14 years; median age, 43.5 years). All except 2 patients were symptomatic: 99 patients (77%) were in NYHA functional class III or IV (Table 1⇓).

Mitral CBC Procedure

Percutaneous mitral CBC was performed as previously described; the double-balloon technique8 was used in 83 patients, and the Inoue balloon4 was used in 49 patients in the later part of our experience. All patients had previously undergone clinical, echocardiographic/Doppler ultrasound evaluation and complete diagnostic cardiac catheterization and angiography to determine whether the patients needed interventional therapy for their MS.89 Complete right- and left-heart catheterization with determination of intracardiac and intravascular pressures, arterial and venous blood oxygen saturations by oximetry, and CO were performed immediately before and after CBC. CO was calculated according to the Fick principle with measured body oxygen consumption and, in most patients, also with thermodilution. Blood oxygen saturations were also determined after CBC to detect interatrial left-to-right shunts. The MVA was calculated both immediately before and after CBC according to the Gorlin formula23 using the CO determined with the Fick principle. Follow-up cardiac catheterization/angiography was performed in 68 patients between 3 and 6 months after CBC, in most as part of a research protocol.

Echocardiographic/Doppler Ultrasound Evaluation

M-mode and two-dimensional echocardiography and Doppler ultrasound were performed usually ≤24 hours before CBC and initially both immediately and 24 hours after CBC.924 Additional studies were performed at 3 to 6 months in many patients, at 12 months after CBC, and annually thereafter. Transesophageal echocardiography was also performed before CBC in many patients in the past few years, mainly to exclude the presence of LA thrombus and also, in some patients, to obtain a better view of the mitral valve. The presence of MR was defined as a high-velocity jet that occurred in systole and extended from the mitral valve into the left atrium. Evaluations were made from the apical four-chamber view. The Doppler sample volume was moved throughout the entire left atrium to identify the maximal extent of the regurgitant jet. The regurgitant jet was graded as 1+ to 4+. The morphological features of the mitral valve were categorized as was previously described (USC scoring system).24 Each echocardiogram was evaluated with respect to valvular mobility and thickening, calcification, and subvalvular thickening. A score was assigned for each feature on a scale ranging from 0 to 2; leaflet motion and thickness were the only two echocardiographic features of the mitral valve morphology that were shown to be predictive of the immediate post-CBC MVA.24 To provide consistency in the echocardiographic readings, all echocardiograms were evaluated by one of the authors (Dr Kawanishi), who also rereviewed all of the early echocardiograms.

Follow-up Studies

Early follow-up was performed for clinical care at 2 to 4 or 4 to 6 weeks or as frequently as was clinically indicated. Subsequent clinical follow-up data were obtained at 3 to 6 months and at 12 months after CBC and at 1-year intervals thereafter as part of the research protocol; data were obtained more frequently for clinical care purposes if indicated. Predefined end points of follow-up and of events were death, MVR, or repeat CBC. All patients were seen in the Griffith Teaching/Research Center. Exercise treadmill tests (Bruce protocol)25 were performed in many patients before CBC as well as at 3 months and 1, 2, 3, and 4 years after CBC. Telephone interviews were conducted when visits to the Griffith Center were logistically impossible.

Statistical Analysis

Data are reported as mean±SD. A value of P≤.05 was considered to indicate statistical significance. Continuous data (eg, exercise treadmill times) were compared with the use of paired-sample t test. Kaplan-Meier estimates were used to determine total survival and event-free survival (defined as the absence of repeat CBC, MVR, or death).2627 The first event (repeat CBC, MVR, or death) was considered to be an end point, and the patient was censored. However, for clinical interest, survival data that include deaths after MVR are also presented. Survival analysis was based on all 132 patients in whom the procedure was attempted.

To identify independent predictors of event-free survival, multiple stepwise (forward conditional) Cox regression analysis was performed with significant variables from the continuous univariate analysis. A model was constructed containing only baseline (postprocedural) variables. A second model was constructed that contained postprocedural variables, and both models were tested for two- and three-way interactions. The validity of the proportionality assumption was verified graphically.28 The two significant multivariate postprocedural predictors were entered into Kaplan-Meier survival analysis to determine event-free survival according to subgroup at 1, 2, 3, 4, 5, 6, and 7 years.

Results

Immediate

Baseline clinical and echocardiographic characteristics of the study population are summarized in Table 1⇑. CBC was completed successfully in 126 of the 132 patients (95%) in whom it was attempted. There were 6 (4.5%) “hospital deaths” (≤1 month after procedure). The causes of death were acute pulmonary edema/cardiogenic shock (1 functional class IV patient), LV perforation (2 patients), cardiac arrest during induction of anesthesia for MVR for acute 4+ MR (1 patient), cardiac arrest during attempted emergency CBC after resuscitation from a cardiac arrest (1 patient who was previously in functional class IV), and death after arrival in emergency department in a comatose state at 30 days after successful CBC, secondary to a cerebrovascular accident (possibly embolus or hemorrhage) (1 patient). In the past 4.5 years of the study during which CBC was performed in 69 of 132 patients (52%), the success rate was 100%, and there have been no hospital deaths.

In the 99 patients in whom MR was assessed by angiography immediately before and after CBC, the degree of MR was unchanged in 49 patients, increased by 1 grade in 17 patients, increased by 2 grades in 13, increased by ≥3 grades in 7, and decreased in 13 patients (Table 2⇓). After CBC, grade 3 or 4 MR was present in 6 of the 99 patients.

Follow-up

Follow-up data for an average period of 29±29 months (range, 0 to 100 months) were available for all patients in whom CBC was attempted. Patients followed for 0 months were either “hospital” deaths or patients who left the country after the procedure. Among the 126 patients in whom the procedure was successfully completed, 25 (20%) had persistence or recurrence of symptoms that necessitated repeat CBC in 6 (4.5%) at an average time of 17±23 months (median, 9 months) after CBC and MVR in 19 (15%) at an average time of 18±25 months (median, 7 months) after CBC. After exclusion of patients who either had an event and were censored or were not available for follow-up at the last observation date, 73 patients remained available after 1 year for further observation, 58 remained at the end of 2 years, 44 remained at the end of 3 years, 34 remained at the end of 4 years, 25 remained at the end of 5 years, and 15 and 9 patients remained at the end of 6 and 7 years, respectively.

Of the 132 patients, there were 6 hospital deaths, and 3 patients were confirmed to have left the country; the follow-up period of the remaining patients was for 32.4±29.2 months (median, 24 months). Twenty-five patients reached a study end point (repeat CBC or MVR); follow-up for clinical care is available in these patients. Of the remaining 98 patients who have not reached a study end point, 77 (79%) had current follow-up at the time of data analysis; follow-up time of these patients was 41.7±27 months (median, 37 months), and in the 21 patients who were lost to follow-up, the follow-up time was 21.6±27 months (median, 7 months) before being lost to follow-up.

MVR or repeat CBC was performed in 25 patients (20%); all of these patients were in NYHA functional class III or IV. MVR was performed in 19 patients (15%). The indications for MVR were a persistence or recurrence of symptoms associated with an unsatisfactory result of CBC. Of the 19 patients, after CBC, 5 patients had MR grade 3 or 4, 7 had an immediate post-CBC MVA of <1.5 cm2, and 7 patients had an immediate post-CBC MVA of ≥1.5 cm2 (of these 7, 6 had a mean PAWP of >18 mm Hg, and the post-CBC mean PAWP was not recorded in 1). Repeat CBC was performed in 6 patients (5%). The indications for repeat CBC were the same as for MVR; however, the valve was considered suitable for repeat CBC because of a low echocardiographic score and the absence of grade 3 or 4 MR. The repeat CBC was successful in each instance.

The actuarially determined overall survival rate at 7 years was 95±1% (Fig 1⇓). When mortality after MVR (four deaths) was included, survival at 2 and 7 years was 93±2% and 83±6%, respectively (see Statistical Analysis). The probability of event-free survival (survival without MVR or repeat CBC) was 80±4% at 1 year, 77±4% at 3 years, and 65±6 at 7 years (Fig 1⇓).

Actuarial curves showing the probability of survival and event-free survival (survival without MVR or repeat CBC) after CBC for MS. The post-MVR mortality is not included (see text). The number of patients available for survival analysis at the end of each year of follow-up was 73, 58, 44, 34, 25, 15, and 9, respectively.

There were no strokes and no systemic emboli except for the one hospital death at 30 days; patients who were in atrial fibrillation were treated with long-term anticoagulants.

At 3 months after CBC, 59% of patients were in functional class I, 30% were in class II, 10% were in class III, and 1 patient was in class IV. The percentage of patients in functional class III and IV at 1, 5, and 7 years of follow-up was 6%, 22%, and 0%, respectively. All functional class III and IV patients were offered MVR or repeat CBC; thus, those in functional class III and IV varied from year to year. Some patients who were offered MVR refused the procedure. At last follow-up, of 77 patients (above), 6 (7.8%) were in functional class III, and the remaining patients were in functional class I and II.

The treadmill time (seconds) for patients in functional class I or II before CBC was 435±179 (n=22) versus 330±151 (n=78) for those in functional class III or IV (P=.007) (Table 3⇓). At 3 months after CBC, treadmill time for patients in functional class I or II was 501±190 (n=61) compared with 236±149 (n=7) for patients in functional class III or IV (P<.001). The treadmill times of the patients at 1, 2, 3, and 4 years after CBC are shown in Table 3⇓. Patients who were in NYHA functional class I or II had significantly longer exercise treadmill times at 3-month and 1- and 2-year follow-up than those in functional class III or IV (Table 3⇓).

As categorical variables, one baseline and seven postprocedural variables were significant univariate predictors of long-term outcome. The predicted rates of event-free survival for subgroups defined according to these variables were estimated at yearly intervals (Table 4⇓).

Categorical Predictors of Event-Free Survival After CBC According to the Univariate Analysis

Multivariate Analyses

In contrast to the baseline variables, when hemodynamic variables measured immediately after the procedure were included in the stepwise multivariate analysis, the post-CBC MVA (P=.003) and post-CBC mean PAWP (P=.001) emerged as the only statistically significant predictors of long-term outcome. None of the baseline variables in the predictive model were significant factors in the determination of long-term outcome. Actuarial event-free survival after CBC was 75±7% at 7 years in 96 patients with MVA of ≥1.5 cm2 versus 32±12% in 24 patients with MVA of <1.5 cm2 (P<.001) (Fig 2⇓).

Actuarial curves showing the probability of event-free survival after CBC for MS according to the immediate post-CBC MVA of ≥1.5 cm2 versus <1.5 cm2.

Patients with MVA of ≥1.5 cm2 (n=96) could be further divided into high- and low-risk subgroups for 7-year event-free survival by three post-CBC variables. In patients with MVA of ≥1.5 cm2 and mean PAWP of ≤18 mm Hg, the actuarial 7-year survival was 90±6% versus 48±14% in those with MVA of ≥1.5 cm2 and mean PAWP >18 mm Hg (P=.0002) (Fig 3⇓). In patients with post-CBC MVA of ≥1.5 cm2 and CI of ≥2.5 L·min−1·m−2, the actuarial 7-year event-free survival was 82±8% versus 61±13% in those with a CI value of <2.5 L·min−1·m−2 (P=.004) (Fig 4⇓). Patients with MVA of ≥1.5 cm2 and mean PAP of <30 mm Hg had an actuarial 7-year event-free survival rate of 89±6% versus 61±12% in those with mean PAP of ≥30 mm Hg (P=.09). Patients whose post-CBC MVA was <1.5 cm2 (n=24) had no additional predictors of event-free survival.

Actuarial curves showing the probability of event-free survival after CBC for MS according to the immediate post-CBC MVA of ≥1.5 cm2 and CI of ≥2.5 versus 2.5 L·min−1·m−2.

Discussion

Our study demonstrates that CBC for MS was successfully completed in 95% of patients in whom it was attempted. The actuarial 7-year survival was 95±1%; the event-free survival was 65±6%. Independent predictors of event-free survival on multivariate analysis were MVA of ≥1.5 cm2 and mean PAWP of ≤18 mm Hg immediately after the CBC; the best subgroup of patients were those who had an MVA value of ≥1.5 cm2 and a mean PAWP of ≤18 mm Hg. Most of the patients were functionally improved initially; this improvement was largely maintained on further follow-up and was documented by an increase in exercise treadmill times.

The overall success rate was 95%, which is similar to that reported by others.3132 The “hospital” (30-day) mortality rate was 4.5%. Both of these were at least partly related to a “learning phase” with regard to selection of suitable patients for the procedure and reduction in complications, such as perforation of the left ventricle. In the past 4.5 years of the study during which CBC was performed in 69 patients (52%), the success rate has been 100% and there have been no hospital deaths. The early death rate is similar to that observed by other investigators (from 1% to 9%) and in the multicenter NHLBI Registry (3%)19313233 (also see below). Of the six hospital deaths in our study, one was due to an out-of-hospital cerebrovascular accident (possibly embolus or hemorrhage) 30 days after CBC, and one occurred in a patient who was in extremis before the CBC. The hospital mortality for closed surgical commissurotomy in the early era of surgery ranged from <1% to 19%343536 and later dropped to 3.4% and 3.7%.37383940 Subsequently, the operative mortality of closed/open surgical commissurotomy in the late 1960s to mid-1984 ranged from 0% to 2.3%.41424344454647484950 Patients entered into randomized trials of CBC versus surgery after the “learning phase” of CBC was at least partly completed, the hospital mortality of CBC and of surgical commissurotomy were not significantly different.10111213

We previously documented that at 3 months after CBC, patients maintain the increase in MVA as well as the reductions in mean PAWP and mean PAP, not only at rest but also at an increased level of exercise.9 In a preliminary report, we showed that these hemodynamic improvements were still present at 3 years after CBC.51 The lower mean PAWP (indirect LAP) at exercise is the major hemodynamic reason9 for the observed improvement in symptomatic state (NYHA functional class), which was documented objectively by an improvement in exercise treadmill times9 (Table 3⇑).

The overall actuarial 7-year survival rate was 95±1%. This does not include the four late deaths, all of which were hospital deaths that occurred after MVR, which was performed at an average follow-up time of 18±25 months (median, 7 months). These are not included in the overall survival rate because MVR was an end point of the study; including these deaths, the 7-year survival was 83±6%. In the NHLBI Registry, the patients were also censored at the time of subsequent mitral valve surgery or repeat CBC.52

MVR or repeat CBC was performed in 25 patients (20%; MVR in 19 [15%] and repeat CBC in 6 [5%]). These findings are similar to those reported by others; Cohen et al31 reported that 18% of patients underwent subsequent MVR or repeat CBC, and Palacios et al53 reported that 21% of their patients underwent MVR at 4 years of follow-up.

We previously documented that the use of an objective quantitative echocardiographic scoring system (USC scoring system) of 0 to 4 was the best predictor of the MVA immediately after CBC.24 Similar observations have been made about a subjective semiquantitative echocardiographic (MGH) scoring system1954 ; the r value for a change in MVA after CBC using the latter system was −0.40 in the MGH study55 and −0.15 in the NHLBI Registry.32 Using the USC scoring system, 46% and 51% of patients with a pre-CBC score of 0 and 1 to 2, respectively, achieved a post-CBC MVA of ≥2.0 cm2. Furthermore, 78% and 84% of patients with a score of 0 or 1 to 2, respectively, achieved an MVA of ≥1.5 cm2, but only 3 of 10 patients (30%) with a score of 3 or 4 achieved an MVA of ≥1.5 cm2.

The event-free actuarial 7-year survival was 65±6%; however, in various subgroups, it ranged from 90% to 13% (Figs 2 through 4⇑⇑⇑). By univariate analysis, there were several predictors of event-free survival. However, by multivariate analysis, only two post-CBC variables (MVA of ≥1.5 cm2 and mean PAWP of ≤18 mm Hg) were statistically significant independent predictors of an event-free 7-year survival. Patients with a post-CBC MVA of ≥1.5 cm2 and a mean PAWP of ≤18 mm Hg had the best 7-year event-free survival of 90±6% (Fig 3⇑). In our study, 96 of all patients (73%) achieved an MVA of ≥1.5 cm2, and 59 patients (45%) fit into the category for the best 7-year result (post-CBC MVA of ≥1.5 cm2 and mean PAWP of ≤18 mm Hg). Of interest, patient 29 in our series was age 21 years and in functional class III before CBC and had a mitral valve score of 1, an MVA of 0.70 cm2, and mean PAWP of 32 mm Hg. After CBC, she had an MVA of 2.1 cm2 and a mean PAWP of 14 mm Hg. At 7 years after CBC, she has had 4 uneventful pregnancies and is minimally symptomatic with full unrestricted activity taking care of her family and the house.

Of patients with pre-CBC score of 0 and 1 or 2, 54% and 51% of patients had a post-CBC MVA of ≥1.5 cm2 and mean PAWP of <18 mm Hg, and only 1 patient (10%) with a score of 3 or 4 fit into this best category. The pre-CBC echocardiographic score was not a statistically significant independent predictor of 7-year event-free survival; this is probably because the pre-CBC echocardiographic score is the best predictor of the immediate post-CBC MVA.19202432 Most patients (>80%) with an echocardiographic score of 0, 1, or 2 achieved an MVA of ≥1.5 cm2 immediately after CBC. It is reasonable that the MVA and the hemodynamics present after CBC should represent an excellent and/or best predictor of the subsequent outcome.

Other studies have reported 4- and 5-year results after CBC. Cohen and coworkers31 reported follow-up data on 145 patients for a period averaging 36±20 months. The number of patients available for observation at the end of each time period was not given. The actuarial 5-year survival was 76%, and actuarial event-free survival was 51%, which is lower than that seen in the present study. Palacios et al53 reported on 320 patients who survived the procedure; the follow-up time averaged 20±12 months. On follow-up, after the patients who died or were censored at time of either MVR or development of NYHA functional class III or IV, the number of patients remaining for observation at the end of 1, 2, 3, and 4 years were 218, 106, 36, and 12, respectively. At 4 years, the actuarial survival was 90±4%; the actuarial event-free survival was 66%, with a 95% confidence interval of 57% to 75%. In the preliminary report from the NHLBI Registry,52 at a mean follow-up of 3.2 years, at 4 years the actuarial survival was 84% and the actuarial event-free survival was 60%. The number of patients available for observation at the end of 4 years was 141. Multivariate predictors of mortality included NYHA class IV, higher echocardiographic score, higher postprocedural PA systolic pressure, and higher LVEDP (P≤.01).

It is important to keep in mind that patient-related factors influence the results and outcome of a procedure and the incidence of these factors may be different in the various studies.56 For example, the ages of patients in various US studies were 59±15 years31 and 55±5 years19 ; in the NHLBI Registry, patient age was 54±15 years for women and 55±14 years for men.32 In our study, the patient age was 44±14 years, and the median age was 43.5 years. In a study from France, the age was 43±16 years.20 The ages of the patients in the four randomized trials from Asia and South Africa averaged 19, 27, 30, and 30 years.10111213 The review of Carroll and Feldman16 documented that the mean ages of patients reported from China, Saudi Arabia, India, Korea, and South Africa were in the 20- to 39-year age group16 ; the study from Japan reported patient age as 53±11 years. However, age may not be as important a factor as morphology of the valve; in other words, the patient with a morphologically suitable valve for CBC may get a good result from CBC regardless of the age of the patient. In two of the US studies, 34%31 and 14%19 were in NYHA functional class IV; NYHA functional class IV was present in 13% in the NHLBI Registry and 9% in our study. Most studies do not present “hospital” (ie, 30-day) mortality, as is recommended for surgical studies. In the NHLBI Registry, 64 of the patients (9%) were excluded because of unknown vital status at 30 days.33 The hospital (30-day) mortality in the remaining patients, therefore, was 25 of 674 (3.7%); in year 1 of the registry, it was 5%, and in year 2, it was 2%.32 In our study, the 30-day mortality was 4.5%. However, our study was initiated almost 2 years before the NHLBI Registry; in our study, in the last 4.5 years of the study (when 52% of the patients were studied), there was no 30-day mortality.

The long-term (≤25 years) results of closed surgical commissurotomy are good and are particularly excellent in patients who had characteristics that would make them the best candidates for CBC.57 The long-term results of open versus closed surgical commissurotomy are similar.58 The short-term results from randomized trials of CBC versus closed or open surgical commissurotomy are not significantly different10111213 ; nonrandomized studies yielded similar conclusions.59 Our data show that the 7-year results of CBC are good and are excellent in selected subgroups of patients. These findings of favorable intermediate-term results strengthen the previous conclusions14175358596061 that CBC should be the procedure of first choice in selected patients in centers with experience and skill in performing this procedure.

Addendum

Since submission of our manuscript, Jung and coworkers (J Am Coll Cardiol. 1996;27:407-414) reported on 528 patients who underwent CBC from 1986 to 1992. Forty patients underwent a repeat mitral valve procedure (35 had surgery and 5 had repeat CBC), and 22 were in NYHA class III or IV but did not undergo a reoperation. At 5 years, survival was 93±4%, survival without repeat procedure was 84±6%, and survival without repeat procedure and in class I or II was 76±6% (38 patients at risk).

Selected Abbreviations and Acronyms

CBC

=

catheter balloon commissurotomy

CI

=

cardiac index

CO

=

cardiac output

LA

=

left atrial

LAP

=

left atrial pressure

LV

=

left ventricular

LVEDP

=

left ventricular end-diastolic pressure

MR

=

mitral regurgitation

MS

=

mitral stenosis

MVA

=

mitral valve area

MVG

=

mitral valve gradient

MVR

=

mitral valve replacement

NHLBI

=

National Heart, Lung, and Blood Institute

NYHA

=

New York Heart Association

PAP

=

pulmonary artery pressure

PAWP

=

pulmonary artery wedge pressure

Footnotes

Presented in part at the 44th Annual Scientific Sessions of the American College of Cardiology, New Orleans, La, March 20, 1995.

The National Heart, Lung, and Blood Institute. Complications and mortality of percutaneous balloon mitral commissurotomy: a report from the National Heart, Lung, and Blood Institute Balloon Valvuloplasty Registry. Circulation.1992;86:2014-2024.